Sewing machine



April 13, 1937.

d. o. NELSON 2,077,151

SEWING MACHINE Filed Nov. 19, 1934 '7 Sheets-Sheet 1 i I I;

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April 13, 1937. c. o. NELSON 2,077,151

SEWING MACHINE Filed Nov. 19, 1934 '7 Sheets-Sheet 2 WITNESSES: INVENTOR:

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SEWING MACHINE Filed Nov. 19, 1934 '7 Sheets-Sheet 5 LN v INVENTOR: V

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SEWING MACHINE Filed Nov. 19', 1954 7 Sheets-Sheet 5 FIG; U

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I SEWING MACHINE Filed Nov. 19, 1934' 7 SheetsSheet 6 FIG; A;

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WITNESSES.- I YINVENITOR: Mai 3 Carl 0. TEX/30w,

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April 13, 1937. c O NELSON I 2,077,151

IIIIIIIIIII NE Filed Nov. 19, 1934 i 7 Sheets-Sheet 7 Fla HQ W1 TNESSES:

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Patented Apr. 13 1937 UNITED ST TES snwnvo mcnmr:

' Carl 0. Nelson, Chicago, Ill, assignor to Union Special Machine Company, Chicago, 111., a corporation of Illinois Application November 19,1934, Serial No. 753,671

9 Claims. (01. 112-181) This invention relates to sewing machines and imore particularly to machines of the lockstitch The object of the invention is to provide in a sewing machine of this type, stitch forming mechanism, including an improved rotary hook and bobbin carrier with the elements of the mechanism so formed and interrelated as permit the machine to be operated at a greater speed 10 than has heretofore been possible.

It has been customary with such machines to employ a stationary bobbin holder and a surrounding rotary hook which, incident to its rotation, can'ies the needle-thread loop around the bobbin holder and ultimately releases the loop to form ,the stitch. To provide for the release of the needle thread loop, the annular bearing elements between the rotating and stationary parts of the mechanism are cut away throughout a limited portion of their circumference. -When these out out areas coincide, release of the thread loop is permitted, the take-up mechanism for the needle thread being designed to draw the thread through the opening thus provided. With a machine which is operated at ordinary speeds, the

' release of the needle thread loop over the bobbin holder does not occasion any serious difliculty, but as thespeed of the machine is increased beyond the range of hitherto customary speeds, the release of the needle thread loop cannot be accomplished by the means usually provided for that p p With the higher speeds there is presented on the one hand the problem of providing adequate ssbearing surfaces between the stationary and rotating parts of the hook, for such surfaces must extend substantially throughout the circumference of the hook, and. this imposes a definite limitation upon'expanding the size of the opening 40 through which the needle thread loop is released. On'the other hand, the higher speeds reduce the time interval of the thread release, making it" necessary for the take-up mechanism to draw the needle thread through the opening with a very high linear-velocity. The momentum imparted.

to the needle thrust incident to the upward pull thereon-will cause the thread to break if its movement is obstructed, or if it impinges upon sharp edges in its passage through the opening in the bearing surfaces, and this in turn imposes a definite limitation upon restricting the size of the opening through which the release is eflected." The present invention is characterized by interfltting bearing surfaces between the elements of the rotary hook which are so formed as toit passes. adjacent to the cut away portion thereof isbeveled provide adequate circumferential engagement and v thread loop sufllciently before it attains its maximum take-up velocity,'to prevent the loop from being drawn taut against the surfaces over which Moreover, one of the bearing surfaces upon sharp edges.

Other more specific advantages characteristic of the present invention will become more apparent from the description hereinafter set forth of one embodiment or example of the practice thereof, having reference to the accompanying drawings. Of the drawings:

Fig. I represents a side elevation of a sewing machine embodying my invention, with certain parts cut away for clearness of illustration.

Fig. II represents an end elevation of the same,

with the cover plate removed to reveal the'needle actuating and take-up mechanism.

Fig. 111 represents a view showing parts of the take-up mechanism, the needle, the rotary hook,

and bobbin holder, illustrating the relative posi-' tions of these parts when the take -up' lever is at its maximum elevation.

Fig. IV represents a view similar to Fig. 111,

but showing the relative positions of the parts later in the cycle oi. operation and when theneedle is in its lowermost position.

Fig. V represents a view similar to Fig. 111, but

showing the relative positions of the parts as the needle emerges from the bobbincase in its upward travel. c

' Fig. VI represents a view similar to Fig. III, but

but showing-the relative positions of the parts I after the take-up lever has commenced its upward movement.

Fig. VIII represents a view similar to Fig. III,

but showing the relative positions of the parts just prior to the release of the needle threadf loop from the raceway of the rotary hook.

Fig. 1x represents a view similar to Fig. 11:,

but showing the relative positions of the parts at the point where the needle thread loop is re-/ leased from the raceway of the rotary hook Fig. X represents an enlarged detailed ,view of the rotary hook and bobbin holder showing the .same in the positions occupied at the point of release of the needle thread loop from the raceway.

Fig. XI represents a plan view of the rotaryhook and bobbin holder in the same relative positions as represented in Fig. X.

Figs. XII, XIII and XIV represent enlarged fragmentary views of the rotary hook and bobbin holder with parts thereof cut away, showing respectively the successive positions of the rotary hook before the needle thread loop is released from the raceway, at the point of release, and immediately after such release; and,

Figs. XV, XVI and XVII represent cross-sectional views, taken as indicated by the lines XV-XV, XVI-XVI and XVII-XVIII in Figs. XII, XIII and VI, respectively.

The sewing machine selected for illustration in the "drawings is of the type described in the pending application for U. S. Letters Patent,

' Serial No. 670,186, filed May 9, 1933, of Norman V. Christensen and Charles F. Rubel. As most clearly shown in Fig. I it comprises generally a supporting bed 3I, which serves as the cl th plate of the machine, and a standard 33 h v-, ing an overhanging arm 34. At the end of the overhanging arm, there is mounted a reciprocatory needle bar 35 carrying a needle 35. The needle bar 35 is connected to amain shaft 31, extending within the overhanging arm 34, by means of a crank 38, a crank arm 39, and a link 40, the latter being attached at its lower end to a collar 42 on the needle bar 35. Rotation of the main shaft 31 is accomplished through a belt "pulley 43, and the main shaft 31 is connected through gears 44, 45, 45 with an operating shaft 41 at the base of the machine, which is driven at. the same speed as the main-shaft 31. The movements of the feed mechanism, comprehensively designated at 48, are derived from the operating shaft 41, but such movements are not material to the present invention and are therefore not described herein. An auxiliary shaft 49, carrying a rotary hook 50 is connected to the operating shaft 41 by gears 5I,'52- which are so proportioned that the rotary hook 55 is given two rotations to one rotation of the main shaft 31.

,As most-clearly shown in Fig. II, the take-up mechanism for the needle thread is mounted ,within the end of the overhanging arm 34', and

such mechanism derives its movement from the crank 38 on the main shaft 31. A take-up lever 54 is pivotally attached to the. crank 38 by a pin 55, and intermediate its ends the take-up lever Y 54 is pivotally attached to-a. swinging link 55 fulcrumed at 51. Associated with the take-up mechanism are the usual thread guiding and tensioning devices as indicated at 53, 55, 55, 5|.

At the end of the overhanging arm 34 there is also provided a presser foot 5 2 for holding the material on the work support. By means of a spring 53, the presser foot is yieldingly depressed. An elevating lever 54 is employed for raising the presser foot 52. The parts described above are of usual construction, and it will be apparent thatthis invention may be applied to many different forms of lockstitch machines, and that the particular machine shown in the drawings represents merely-one convenient example "serving to illustrate the practice of the invention.

' each division representing the movement of the take-up lever corresponding to 12 of rotation of the main' shaft 31. The point designated at I has been arbitrarily selected and is the point at which the needle 35 is in its lowermost position. It will be noted that the take-up lever 54 moves downwardly from the point I to the point II with substantially uniform speed and then proceeds upwardly from the point II with accelerating angular velocity. 'At approximately the point I5 the maximum angular velocity is reached, and from there to the point 22, which represents the upper limit of travel, the velocity diminishes. Downward movement from the point 22 to the point I proceeds at a substantially uniform rate. From the take-up lever 54 the needle thread 55 leads downwardly through a needle clamping device 55 to the eye 51 of the needle, and from thence to the work, indicated at 65. From the bobbin holder 59 the bobbin thread 15 leads upwardly through an aperture H in the work plate 12, and from thence to. the work 55. In the example illustrated, in which the rotary hook 50 has two revolutions for each double stroke of the needle bar 35, the position of the rotary hook 50, when the take-up lever 54 is at its upper limit, and while the needle 35 is moving downwardly towards the rotary hook 55, is as represented in Fig. III. In Fig. IV the position of the parts is shown at the point where the needle 36 has penetrated the work 55, the work plate 12 and the bobbin holder 55, and has reached its lowermost position. As the needle 3 35 moves upwardly from this position, and the rotary hook 513 revolves in a clockwise direction, the needle thread 55 is engaged by the beak 13 of the rotary hook, as shown in Fig. V, and a loop is drawn from the needle 35. The loop thus drawn from the needle is represented a "14 in Fig. VI, and is there shown carried pa t way around the stationary bobbin holder 55. In this position the take-up lever 54 has reached its lower limit of travel, and the needle 35 has passed upwardly through the work work 58.

With continued rotation of the rotary hook 55, the loop 14 is drawn up with rapidly accelerating plate 12 and the velocity by the take-up lever 54, and it is shifted from the beak 13 of the rotary hook 55 to thenose .15 which is disposed oppositely thereto. The

parts then assume the positions represented in Fig. VII. The movement of the take-up lever 54 :continues at a gradual speed and tends to con'-' tract the loop 14 to a shape substantially as rep-' rotary hook 55 and the bobbin holder 55, as il1'u sresented-in Fig. VIII. Eventually, the loop'14 is released from bearing elements .between the -trated inFig. IX. The loop 14 is-retained'for an instant upon the nose 15 of the rotary hook il and is finally cast clea'r'of the rot'ary'hook to angular velocity and has not isreleased from the'bearingele form of a cylindrical ring having a peripheral bearing rib 16 which extends substantially around its circumference, but which is cut away or interrupted to form a clearance space 81 through which the needle thread loop may be released. The rib 16 engages with an annular bearing groove on the underside of the rotary hook 50.

The leading end of the peripheral rib 16 adjacent to this clearence space 81 is formed with the usual abrupt shoulder I8 constituting a detaining horn upon-which the thread loop is caught during the first part of its passage around the bobbin holder 69. The trailing end of the peripheral rib I5 is provided with a beveled surface 19 at oneside, and isdesirably tapered downwardly towards the cut away or clearance space 81 through which the thread loop is released. The beveled surface 10 is also inclined transversely in a direction leading downwardly from the needle side of the bobbin holder 69 to the opposite side, and the adjacent I surfaces of-the rib are rounded to 'avoid sharp edges.

It will be particularly observed that the bearing face 80 at the needle-side of the peripheral rib I6 is preserved as a vertical bearing surface extending substantially to the region of the cut out, whereas the bearing face ill at the opposite side is considerably shortened. It is important that the bearing elements between the bobbin holder 69,

and the rotary hook 50 shall have adequate circumferential engagement to prevent excessive vibration and to maintain the proper alignment between these parts. The bobbin holder 69 is held against rotation by means of a notched formation 83 which is loosely engaged by a lug 84. As it is not rigidly fixed in its position, the bobbin holder 89 has capacity for slight movement and is subjected to an axial thrust in a direction towards the lug 84 as the bobbin thread is drawn fromthebobbin casing 85. By preserving the vertical bearing face 80, so that it is substantially coextensive inits circumference, with the length of the rib 16, this thrust is adequately resisted and excessive play between the rib i6 and the bearinggroove 'l'l is direction diagonally upward from the bobbin prevented. Moreover, the bearing groove II extends substantially to the beak 13 at one side of a clearance space 88 through which the thread is released and substantially to the nose 15 at the other side of the opening.

-As appears in Figs. X and XI, at the point where the thread loop 14 is released from the raceway,

the take-up thrust upon the needle thread is in a direction diagonally across the rib 16 towards the needle opening 86 in the bobbin holder 69 and in a holder 69 towards the needle opening 'II in the work plate 12. The beveled surface 19 at the trailing end of the rib 61 is thus inclined to conform 1 substantially to the direction of the pull on the needle thread with the result that the thread loop ii is eased around the end of the rib preparatory to its release, preventing its being drawn taut of its passage.

This condition is more clearly illustrated in Figs. XII, XIII and XIV, from which it will be noted that the thread loop 14 has capacity for appreciable contraction between the point where it is caught around the bearing elements, which is shown in Fig. X11, and the point where it is free to be released from-the raceway, which is shown in Fig. xm. Following the release of the thread loop ll from the raceway, the loop is retained for g 3 against the surface thereof at the critical moment an instant upon the nose 15, as illustrated in Fig. 1

XIV, thus preventing the thread from twisting, and it is ultimately cast completely clear of the a rotary hook.

The cross sectional views represented in Figs.

XV and XVI, also serve to illustrate how the needle thread loop I4 is eased over the trailing end of the rib 16 with the loop riding up onthe beveled surface 19 immediately'prior to its release.

The difficulty whichhas heretofore been experienced with rotary hooks in attempting to operate lockstitch machines at higher than customary speeds is that the thread is drawn taut and stretched beyond its elastic limit before it is released from the rotary hook, with resultant breaking of the thread. When a sewing machine is operated at a speed of say, 5000 revolutions of the main shaft per minute, it will be appreciated that the thread is taken through the needle eye at a very high velocity--it may be in excess of 100' miles an hour at the point of maximum speedand if the release of the thread loop does not ocour until after this speed is reached, there will be a pronounced jerk at the bight of the thread which extends around the bearing elements. If at this point any interference is offered to the free movement of the thread or to the contraction of the thread loop, the thread will break.

By forming the bearing elements of the rotary hook and bobbin holder in the manner of this invention, and by advancing the timeof the release of the thread loop from the raceway, so" that such release takes place before the take-up reaches its maximum velocity, it is possible to operate sewing machines at speeds which have not heretofore been obtained.

While I have described one example of the practice of my invention, with reference to a sewing machine havinga specific form of take-up mechanism and rotary hook, it will be apparent that many changes may be made in the form of the apparatusherein described without departing from the spirit of the invention as defined in the annexed claims.

Having thus described my invention, I claim:

1. In a sewing machine, a rotary hook and a bobbin holder having annular interengaging bearing elements interrupted for a relatively small ,portion of their circumferencestoaflord clearance spaces permitting release oif the needle thread loop as it pass over the bobbin holder, and reciprocatory mechanism, for taking up the needle thread loop with an accelerating velocity, the clearance spaces of said bearing elements being so disposed as to permit release of the .needle thread loop before -it attains its maximum velocity, and one of the bearing elements having the end adjacent to its clearance space shaped to ease the thread loop preparatory to its release, thereby preventing its being drawn taut against the surface of said bearing; element. 2.- In a sewing machine,'a rotary hook and a bobbin holder having a peripheral bearing element engaging said rotary hook throughout the major portion of its circumference, said bearin velocity and being shaped to ease the thread loop l preparatory to its release, thereby preventing its being drawn taut against the trailing end of said bearing element.

3. In asewing machine, a rotary hook and-a bobbin holder having interengaging annular l bearing elements, interrupted for a relatively small portion of their circumferences to afford clearance spaces permitting the release of the needle thread loop as it passes over the bobbin holder, one of said bearing elements being formed 0 adjacent its clearance space with a beveled end over which the needle thread loop is released, take-up mechanism for the needle thread loop,

- and means for reciprocating said mechanism with the velocity of the take-up accelerating during 25 the upward stroke, said beveled end being so disposedas to permit release of the needle thread -loop sufllciently -befor'e it attains its maximum take-up velocity to prevent the needle thread loop from being drawn taut against the surface of 3 said bearing element.

, 4. In a sewing machine, a rotary hook and a bobbinholder having a peripheral rib engaging said rotary hook throughout the major portion of its circumference, said rib being cut away to 35 permit the. release of the needle thread loop as it .passes over the bobbin holder, and having the trailing end thereofformed with a beveled edge over which said needle thread loop is released,

take-up mechanism for the needle thread loop, 40 and means for reciprocating said, mechanism with the velocity of the take-up accelerating during theupward stroke, said trailing end of the rib being so disposed as to permitjrelease of the needle thread loop sufficiently before it attains 45 its. maximum take-up velocity to prevent theneedle thread loop from being drawn taut against said rib. a

5. In a sewing machine, a rotary hook and a bobbin holder having interengaging annular- 55 for the needle thread'loop, one of said bearing elements being formed adiacent to itsclearance space with a tapered end beveled substantially in the direction of thethrust on the needle thread loop incident to its take-up so as to prevent said loop from being drawn taut against an 4 edge thereof.

6. In a sewing machine, a rotary hook, a bobbin holder having a peripheral rib engaging said rotary hook throughout the major portion of its circumference, and take-up mechanism for the needle thread loop, said rib being cut away to permit the release of the needle thread loop as it passes over the bobbin holder, and having the trailing end thereof formed with a beveled surface inclined substantially in the direction of the thrust of the needle thread loop incident to its take-up.

7. In a sewing machine,'a rotary hook, a bobbin holder having a peripheral rib engaging said rotary hook throughout themajor portion of .its circumference, and take-up mechanism for the needle thread loop, saidrib being cut away to permit the release of the needle thread loop as it 'passes over the bobbin holder, and having the trailing end thereof gradually tapered towards the cut away portion and transversely beveled to provide an inclined surface leading downwardly from the needle side of the bobbin holder towards the opposite side thereof.

8. In a sewing machine, a rotary hookformed with an internal bearing groove, a bobbin holder in the form of a cylindrical ring having an opening through which the needle passes and. having a peripheral rib engaging said groove throughout the major portion of its circumference, and takeup mechanism for the needle thread loop, said rib being cut away to permit'the release of the needle thread loop as it passes over the bobbin holder and having the trailing end thereof formed with a surface inclined transversely downward from the needle side of the rib to'the opposite side thereof.

9. In a sewing machine, a rotary hook formed with an internal bearing groove, 8. bobbin holder having an opening through which the needle passes and having a peripheral rib with bearing faces at the sides thereof engaging said groove throughout the major portion of its circumference, and take-up mechanism for the needle thread loop, said rib of the bobbin holder being cut away in the vicinity of the needle opening to permit the release of the needle thread loop.

as it passes over the bobbin holder and having the trailing end thereof formed with the bearing face at. the needle side extending substantiallyto the needle opening and with the opposite bearing face beveled to ease the passage of the needle thread-loop prior to its release.

' CARL O. NELSON. 

